Process of baking carbon electrodes and heating by electricity and combustion.



No. 865,608. PATENTED SEPT. 10, 1907.

E. F. PRICE. PROCESS OF BAKING CARBON ELECTRODES AND HEATING BYELECTRICITY AND COMBUSTION. APPLICATION nun APR. 22, 1905.

2 SHEETSSHEET 1.

I M41711 illllllllll 2;); Nil: 4 a 6llllllIllIlllllIllllII|l||l|lllllml||||lllllflllIllllllllllllllilmllllllllg a I J War-166's I luv/6711507:

d. 264 by 7 Z w No. 865,608. PATENTED SEPT. 10, 1907.

- E. I. PRICE. PROCESS OF BAKING CARBON ELECTRODES AND HEATING BYELECTRICITY AND COMBUSTION.

APPLICATION FILED APR. 22, 1905.

2 SHEETS-SHEET 2.

ya. I

NITED STATES PATENT OFFICE.

EDGAR F. PRICE, OF NIAGABA FALLSJNEW YORK.

PR OCESS OF BAKING dARBON EILIELCYPRODES AND HEATING BY ELECTRICITY. AND

COMBUSTION.

Specification of Letters Patent.

Patented Sept. 10, 1907.

Application filed April 22, 1905. Serial No. 256,888.

tricity and Combustion, of which the following is a specification f InUnited States Letters Patent Numbers 752 357 and 752,358, granted to meFebruary 16, 1904, l have described and-claimed certain processes ofelectrically baking the carbon electrodes which are used in carbid andother electric furnaces. In these processes. the

green or partially baked electrodes are placed around a resistance-coreand within a suitable packing and an electric current is then passedthrough the core and in some cases through the packing and electrodes,which are thereby heated to the required temperature. If

the electrodes are taken directly from the molds or press to theelectric furnace and the baking is effected entirely by electricity, theexpense is greater than when a combustion furnace is employed. If theelectrodes have been initially baked by combustion, they areordinarily'allowed to cool and the heat stored in them is dissipatedand'lost before they are placed in the electric furnace. I v

According to the present process, the electrodes are initially heated byproducts of combustion and while hot are electrically heated to therequired temperature. The electrodes to be baked are'preferably embeddedin a nonoxidizing, refractory packing, supported on the hearth ofa-combustion furnace. The final heating may be effected by an electriccurrent passed through a resistance core, around and in proximity towhich the electrodes are arranged. If an electrically-conductive packingis employed, a portion of the electric current will shunt from the corethrough the packing and electrodes, the resistance of which willincrease the supply of heat; The required temperature may also be produced without employing a core, by arranging the electrodes transverselyin a conductive packing and passing the electric current directlythrough the electrodes and interposed layers of packing. as described inUL S. Patent'749,418, granted January 12, 1904, to F. G. Acheson.

In the electric furnaces now employed for the production of graphite,carborundum and calcium carbid, a considerable portion of the heat isconducted through the charge and furnace walls and lost, therebymateri-' ally decreasing the efliciencyof the furnace and increasing thecost of the product. This loss may be prevented by surl-ounding theelectric furnace with a combustion furnace or heating fiues, and thusmaintaining around the electric furnace a heat bufier or stratum ofproducts of combustion having substantially the same temperature as theouter surface of the electric furnace walls. While the loss of heat fromthe outer surfaces of the walls of the combustion chamber or flues maythen be equal to that normally dissipated from the electric furnace, thelost heat will be supplied by the direct combustion-of fuel and aconsiderable economy will thus be effected. For this reason, in thespecific process of baking carbons heretofore referred to, heatinggasesof the proper temperature are preferably passed around the chargeboth before and during the period of electric heating, the initialheating being thus effected solely by the combustion of fuel and the.final heating jointly by combustion and electricity.

Referring to the accompanying drawings-Figure l is a horizontal sectionthrough a furnace for baking electrodes, with the electrodes, packingand resistance core in place, on the line II of Fig. 2; Fig. 2 is atransverse vertical section on the line II-II of Fig. 1 and Fig. 3 is ahorizontal section through a similar furnace in which the electrodes areplaced transverse to the path of the electric current. I i

The combustion furnace may be 'ofany usual or preferred type, that showncomprising side walls 1, end walls 2 and a hearth 3. The side wallscontain-door openings 4 which are brickedup during the operation of thefurnace. The hearth contains longitudinal, parallel flues 5, whichreceive and carry hot products of combustion and deliver them into thefurnace chamber through openings 6 at one end. The products I thencepass longitudinally through the furnace and escape from the other endthrough a stack, not shown.

In the furnace shown in Figs. 1, 2, the carbon electrode bars 7 areplaced end to end within a refractory non-oxidizing packing 8, which mayconsist either of granular coke, anthracite coal or' other materialwhich is electrically conductive or will be converted into a conductorwhen heated, or of a nonconductor,- such as magnesia or sand; Theelectrodes are grouped around a central resistance conductor 9, whichmay be of broken coke, the ends of which are in contact with electricterminals 10, preferably carbon bars, extending through theend walls ofthe furnace. The electrodes, packing and core are supported on thefurnace hearth between side and end walls 11, preferably of tile, whichare spaced away from the side and end walls of the furnace. In employingthis furnace to carry out the process, the molded electrodes, packingand core are placed in position and hot products of combustion arepassed through the hearth-fines and furnace chamber, therebyinitiallyheating the electrodes, packing and resistance conductor and increasingthe'electrical conductivity of each. An electric '7 by the heat radiatedfrom the core and by the current shunted through the packing andelectrodes, if a con ductive packing be employed. It is preferable tosimultaneously'supply hot products of combustionto the furnace and passelectric current through the core, the baking being thereby quickly andeconomically effected. The maximum economy is generally effected bysupplying heating gases during the second stage of the process at atemperature at least equal to that of the surfaces from which theelectrically-generated heat would otherwise be dissipated. If the gasesare below this temperature, electric heat is lost, and if they are aboveit the transfer and loss of heat through the outer furnace-walls isunnecessarily increased. I I i The furnace shown in Fig. 3 is identicalwith that previously described, but the resistance core is omitted andthe electrodes 7 are placed transversely within anelectrically-conductive packing 8. The end electrodes are in contactwith the terminals 10 and the electric heating is effected by theresistance of the electrodes and packing, only.

Carbon electrodes can be baked at a much lower cost by the presentprocess than by those described in my previous patents, since theinitial heating is effected at a relatively low cost by combustion offuel while the final high temperature is obtained by electricity, theheat supplied by combustion nevertheless being retained. The initialheating is also advantageous in that it increases the electricalconductivity of the electrode-bars, packing and core, if used, therebyenabling the electric current to be supplied at a lower potential. Theelectrodes to be baked may themselves constitute the resistancecbnductors specified in claim 1.

I claim:- I

1. The process of baking carbon electrodes, which consists in initiallyheating the electrodes and a resistance conductor or conductors bycombustion, and heating the liot'electrodes to a higher temperature-bypassing an electric current through said conductor or conductors, as setforth.

2. The process of baking carbon electrodes, which consists in placingthe electrodes in proximity to a resistance conductor, initiallyheating'the electrodes by combustion, and heating the hot electrodes toa higher temperature by passing an electric current throughv saidresistance conductor-{as set forth.

3. The process of baking carbon electrodes, which consists in initiallyheating the electrodes by combustion, and heating the hot electrodes toa higher temperature by passing an electric current through them, as setforth.

4. The process of bakingcarbon electrodes, which consists in placing theelectrodes in proximity to a resistance conductor, initially heating theelectrodes and resistance conductor by combustion, and heating the .hotelectrodes to a higher temperature by passing an electric currentthrough said resistance conductor and electrodes, as set forth.

5. The process of baking carbon electrodes, which consists in placingthe electrodes transverse to the path of current-flow, with intermediatelayers of an electricallyconductive packing, initiallyheating theelectrodes by combustion, and heating the hot electrodes to a highertemperature by passing an electric current through said electrodes andpacking, as set forth.

- 6. The process of baking carbon electrodes, which consists inembedding the electrodes transverse to the path of current-flow in anelectrically-conductive packing, initially heating the electrodes bycombustion, and heating the hot electrodes to a higher temperature bypassing an electric current through said electrodes and packing, as

set forth. I

' 7. The process of baking carbon electrodes, which con sists ininitially heating the electrodes by combustion, heating the hot'electrodes to a higher temperature by electricity, and preventing theescape of electricallygenerated heat by a gaseous medium heated bycombustion, as set forth.

8. The process of baking carbon electrodes, which con sists in initiallyheating the electrodes by combustion, heating the hot electrodes to ahigher temperature by passing an electric current through a resistanceconductor, and preventing the escape-of electrically-generated heat bymaintaining hot products of combustion around the zone of electricheating, asset forth.

9. The process of baking carbon electrodes, which consists in initiallyheatingthe electrodes by combustion, heating the hot electrodes to ahigher temperature by passing an electric current through a resistanceconductor, and maintaining in contact with the surfaces which tend todissipate electrically-generated heat, products of combustion having atemperature substantially equal to that of said surfaces, as setforth.

In testimony whereof, I 'ai'flixv my signature in presence of twowitnesses.

EDGAR F. PRICE.

Witnesses:

C. C. Mosrrna, D. Bunonss.

